Optical system for a particle analyzer and particle analyzer using same

ABSTRACT

A compact optical system for a particle analyzer and particle analyzer using same are provided. The optical system for a particle analyzer of the present invention comprises a light source, an irradiation optical system for irradiating particles passing through a flow cell with light from the light source, a photodetector for receiving the scattered light from the particles, a light shielding member for blocking the direct light from the light source from impinging the photodetector, and a detecting lens for directing the scattered light toward the photodetector, wherein the irradiation optical system forms a first focus that focuses the light from the light source on the particle passing through the flow cell, and forms a second focus that focuses the light from the light source at a position between the detecting lens and photodetector, and disposes the light shielding member at the position of the second focus.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/881,323 filed on Jul. 26, 2007 which claims priority under 35 U.S.C.§119 to Japanese Patent Application No. JP2006-209263 filed Jul. 31,2006, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to an optical system for a particleanalyzer and a particle analyzer using this optical system.

BACKGROUND OF THE INVENTION

Methods using flow cytometers are generally known as methods fordetecting hemocytes in blood and the tangible constituents found inurine and the like.

Flow cytometers analyze particles by irradiating particles flowing in aflow cell, and detecting optical information from the particles.

For example, flow cytometers provided with the optical system shown inFIGS. 1A and 1B are known (U.S. Pat. No. 4,577,964). The optical systemshown in FIG. 1A is configured by a laser 101, beam separator 102,photodetector 103, a lens pair 106 including cylindrical lenses 104 and104, obstacle 113 such as a wire or the like, microscope objective lens115, opaque screen 117, lens 118, and photodetector 119. FIG. 1B showsthe light path of the incident radiation from the laser 101 that haspassed through the cylindrical lenses 104 and 105.

Light from the light source laser 101 is focused at points 112 and 114by the cylindrical lenses 104 and 105. Point 112 is focused on the cellspassing through the channel 107. Point 114 is focused on the wire 113.That is, the wire 113 blocks all the light from the lens pair 106directly through the point 112. Thus, the direct light from the lenspair 106 is blocked by the wire 113. At point 112, the light scatteredby the cells (scattered light) passes the wire 113 and reaches themicroscope objective lens 115. The scattered light is collected by theobjective lens 115 at the aperture 116 formed on the opaque screen 117.The aperture 116 is positioned in the center of the image plane of theobjective lens 115. Therefore, only the scattered light passes throughthe aperture 116 and reaches the photodetector 119.

In recent years, demand has increased for compact analyzers providedwith flow cytometers, for example, blood analyzers. In the opticalsystem of the flow cytometer disclosed in U.S. Pat. No. 4,577,964, aspace is required to dispose the light shielding member of the wire 113between channel 107 of the flow cell and the microscope objective lens115, which functions as a detecting lens. Therefore, the distance islengthened between the channel 107 and the microscope objective lens115. Moreover, a predetermined distance is required between thephotodetector 119 and the microscope objective lens 115 to ensure asuitable optical magnification in the photodetector 119. Thisrequirement resulted in problems inasmuch as the longer distance madethe detector unit larger, as well as the particle analyzer itself.

SUMMARY OF THE INVENTION

The scope of the present invention is defined solely by the appendedclaims, and is not affected to any degree by the statements within thissummary.

An object of the present invention is to provide an optical system for aparticle analyzer that is compact compared to the optical systems usedin conventional particle analyzers, and a particle analyzer that usesthis compact optical system.

That is, the present invention provides:

(1) an optical system for a particle analyzer comprising a light source,an irradiation optical system for irradiating particles passing througha flow cell, a photodetector for receiving the light from the particles,a light shielding member for blocking the direct light from the lightsource entering into the photodetector, and a condenser lens fordirecting the light toward the photodetector, wherein the irradiationoptical system forms a first focus that focuses the light from the lightsource on the particle passing through the flow cell, and forms a secondfocus that focuses the light from the light source at a position betweenthe condenser lens and photodetector, and disposes the light shieldingmember at the position of the second focus;

(2) the optical system for the particle analyzer of (1) or (2), whereinthe irradiation optical system forms a third focus focusing light fromthe light source at a position between the flow cell and the lightsource, and forms the second focus by imaging the third focus using thecondenser lens;

(3) the optical system for the particle analyzer of (1), wherein theirradiation optical system forms the first focus of the light from thelight source that converges in a parallel direction relative to adirection of passage of the particles and extends in a perpendiculardirection relative to the direction of passage of the particles, andforms the second focus that converges in a direction perpendicular tothe direction of passage of particles and extends in a paralleldirection relative to the direction pf passage of particles;

(4) the optical system for the particle analyzer of (2), wherein theirradiation optical system forms the first focus of the light from thelight source that converges in a direction parallel to a direction ofpassage of particles and extends in a perpendicular direction relativeto the direction of passage of particles, and forms the third focus thatconverges in the perpendicular direction relative to the direction ofpassage of the particles and extends in the parallel direction relativeto the direction of passage of the particles;

(5) the optical system for the particle analyzer of any one among (1)through (4), wherein the irradiation optical system has at least onecylindrical lens;

(6) the optical system for the particle analyzer of any one among (1)through (5), further comprising a beam splitter disposed between thedetecting lens and the light shielding member, a second photodetectorfor receiving part of the light split by the beam splitter, and a secondlight shielding member disposed between the beam splitter and the secondphotodetector;

(7) the optical system for a particle analyzer of (6), wherein the lightshielding member having a different scattering angle range for thetransmitted light is disposed relative to the light path split by thebeam splitter;

(8) the optical system for a particle analyzer of any among (1) through(5) have a dichroic mirror disposed between the detecting lens and thelight shielding member, and have a fluorescence detector for receivingfluorescent light split by the dichroic mirror;

(9) a particle analyzer comprising a flow cell through which particlespass, a light source, an irradiation optical system for irradiating theparticles passing through a flow cell, a photodetector for receiving thelight from the particles, a light shielding member for blocking thedirect light from the light source entering into the photodetector, adetecting lens for directing the light from the particles toward thephotodetector, and an analyzing part for analyzing particles based ondetection signals detected by the photodetector, wherein the irradiationoptical system forms a first focus that focuses the light from the lightsource on the particle passing through the flow cell, and forms a secondfocus that focuses the light from the light source at a position betweenthe detecting lens and photodetector, and the photoreceiving opticalsystem provides a light shielding member at the position of the secondfocus;

(10) the particle analyzer of (9), wherein the irradiation opticalsystem forms a third focus focusing light from the light source at aposition between the flow cell and the light source, and forms thesecond focus by imaging the third focus using the detecting lens;

(11) the particle analyzer of any one among (9) and (10), wherein theirradiation optical system forms the first focus that converges thelight from the light source in a direction parallel to the direction ofpassage of the particles, and extends in a perpendicular directionrelative to the direction of passage of the particles, and the secondfocus that converges the light from the light source in the directionperpendicular to the direction of passage of the particles, and extendsin the parallel direction relative to the direction of passage of theparticles; and

(12) the particle analyzer of (10), wherein the irradiation opticalsystem forms the first focus of the light from the light source thatconverges in a direction parallel to the direction of passage ofparticles and extends in a perpendicular direction relative to thedirection of passage of particles, and forms the third focus thatconverges in the perpendicular direction relative to the direction ofpassage of the particles and extends in the parallel direction relativeto the direction of passage of the particles.

The present invention provides a compact optical system for a particleanalyzer and particle analyzer using same. The present inventionrealizes a compact optical system that does not increase cost orcomplexity of the mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 briefly shows an optical system in a conventional flow cytometer;

FIG. 2 briefly shows the structure of a particle analyzer;

FIG. 3 is a side view of the detection part provided with a firstembodiment of the optical system of the particle analyzer of the presentinvention;

FIG. 4 is a top view of the detection part provided with a firstembodiment of the optical system for a particle analyzer of the presentinvention;

FIG. 5 shows a light shielding plate;

FIG. 6 is a top view of the detection part provided with a secondembodiment of the optical system of the particle analyzer of the presentinvention;

FIG. 7 shows a light shielding plate in which the light shielding parthas a different width;

FIG. 8 shows a light shielding pate in which the width of the lightshielding part and the diameter of the circular aperture are different;

FIG. 9 shows the scattering angle characteristics related to scatteredlight intensity and angle;

FIG. 10 is a top view of the detection part provided with a thirdembodiment of the optical system of the particle analyzer of the presentinvention;

FIG. 11 is a top view of the detection part provided with a fourthembodiment of the optical system of the particle analyzer of the presentinvention;

FIG. 12 is a top view of the detection part provided with a fifthembodiment of the optical system of the particle analyzer of the presentinvention;

FIG. 13 is a side view of the detection part provided with a sixthembodiment of the optical system of the particle analyzer of the presentinvention; and

FIG. 14 is a top view of the detection part provided with a sixthembodiment of the optical system of the particle analyzer of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2 shows an embodiment of the structure of the particle analyzer ofthe present invention. The particle analyzer 1 of FIG. 2 is configuredby a measuring unit 2 and analyzing unit 3. The measuring unit 2includes a detection part 4 and controller 5. The detection part 4 isprovided with a flow cell, an irradiation optical system 6 forirradiating particles passing through the flow cell 7 with laser light,a detecting lens 8 for guiding the scattered light from the particlestoward a photodiode 10, a light shielding plate 9 for blocking thedirection light from the irradiation optical system 6, and a photodiode10 for receiving the scattered light from the particles. The controller5 transmits the light signals detected by the photodiode 10 as digitalsignals to an information processing unit 31 of the analyzing part 3.The information processing unit 31 of the analyzing part 3 processes andanalyzes the digital signals which reflect the characteristics of theparticles. The processing and analysis results obtained by theinformation processing unit 31 are displayed on an output unit 32. Afirst embodiment of the optical system for a particle analyzer of thepresent invention is described hereinafter using FIGS. 3 and 4.

FIG. 3 is a side view, and FIG. 4 is a top view (viewed from the top ofthe diagram of FIG. 3) of the detection part 4. The detection part 4shown in FIGS. 3 and 4 is configured by an irradiation optical system 6,flow cell 7 provided with a channel in which particles flow in the ydirection, photodiode 10 for receiving scattered light from theparticles, spherical detecting lens 8 for focusing the scattered lightfrom the particles on the photodiode 10, and light shielding plate 9 forblocking the direct light which passes through the flow cell 7.

The irradiation optical system 6 is provided with a laser diode 61 as alight source, collimator lens 62 for converting the laser light emittedfrom the laser diode 61 to parallel rays, convex cylindrical lens 63 forfocusing the light impinging the collimator lens 62 in a horizontaldirection (direction perpendicular to the flow of the flow cell), andspherical condenser lens 64 for focusing the light from the convexcylindrical lens 63 on the flow cell 7.

In FIGS. 3 and 4, the light path of the direct light emitted from thelaser diode 61 is indicated by dashed lines. The light path of thescattered light from the particles flowing in the flow cell 7 isindicated by solid lines.

Also in FIGS. 3 and 4, the z direction is a direction parallel to theoptical axis of the laser light. The y direction is perpendicular to thez direction, and is parallel to the channel of the particles passingthrough the flow cell 7. The x direction is perpendicular to both the zdirection and y direction. The y direction is referred to theperpendicular direction, and the x direction is referred to as thehorizontal direction hereinafter as viewed from the laser diode 61 side.

When viewing the detection part 4 from the side (refer to FIG. 3), theradial laser light emitted from the laser diode 61 is converted toparallel rays by the collimator lens 62. These parallel rays are notrefracted as they pass through the convex cylindrical lens 63. Then, theparallel rays that have passed through the convex cylindrical lens 63are focused at a first focusing point A in the center of the particleflow of the flow cell 7 by the condenser lens 64. The first focusingpoint A is positioned at or near the focus of the condenser lens 64. Thebeam at the first focusing point A is hyperelliptic in shape (the shapeof the beam viewed from the laser diode 61 side), converging in theperpendicular direction (y direction) and extending in the horizontaldirection (x direction). The direct light that has passed through thefirst focusing point A is masked by the light shielding plate 9.However, the scattered light from the particles is focused by thedetecting lens 8 and impinges the photodiode 10.

When viewing the detection part 4 from above (refer to FIG. 4), theradial laser light emitted from the laser diode 61 is converted toparallel rays by the collimator lens 62. These parallel rays are focusedat a second focusing point B in front of the flow cell 7 by the convexcylindrical lens 63 and condenser lens 64. The beam at the secondfocusing point B is hyperelliptic in shape (the shape of the beam viewedfrom the laser diode 61 side), converging in the horizontal direction (xdirection) and extending in the perpendicular direction (y direction).The laser light that has passed through the second focusing point B isfocused at a third focusing point C by the detecting lens 8. The beam atthe third focusing point C is hyperelliptic in shape (the shape of thebeam viewed from the laser diode 61 side), converging in the horizontaldirection (x direction) and extending in the perpendicular direction (ydirection).

The light shielding plate 9 is positioned at the third focusing point C.As shown in FIG. 5, the light shielding plate 9 has a circular aperture92 formed in the center part, and is provided with a wire-like lightshielding part 91 in the center of the circular aperture 92. The lightshielding part 91 vertically sections the circular aperture 92 byextending in the perpendicular direction (y direction), and has a narrowwidth in the horizontal direction (x direction). As previouslymentioned, the beam at the third focusing point C is hyperelliptic inshape, converging in the horizontal direction (x direction) andextending in the perpendicular direction (y direction). Therefore, thelaser light (direct light) is completely blocked by the light shieldingpart 91. The scattered light from the particles at the first focusingpoint A is focused by the detecting lens 8, and impinges the photodiode10 through the circular aperture 92 of the light shielding plate 9.

In FIG. 5, the maximum scattering angle at which the photodiode 10receives light is defined by the length of the diameter a-a′ of thecircular aperture 92 of the light shielding plate 9. Moreover, theminimum scattering angle at which the photodiode 10 receives light isdefined by the length of the width b-b′ of the wire-like light shieldingpart 91. Therefore, a light shielding plate may be used which has asuitable a-a′ value and b-b′ value for the object being measured. Thelight shielding plate 9 can be easily formed by processing a metal plateor the like coated with a black color.

The present invention does not require that the light shielding plate 9is disposed between the flow cell 7 and the detecting lens 8. Therefore,the distance between the flow cell 7 and the detecting lens 8 can beshortened.

For example, in the conventional art, when scattered light fromparticles is received by the photodiode 10 at an optical magnificationof 20-fold using a detecting lens 8 with a focal length of approximately8 mm, the photodiode 10 must be positioned a distance of 160 mm from thedetecting lens 8. In the present embodiment, however, space is notrequired for the light shielding plate 9. Thus, when scattered lightfrom particles is received by the photodiode 10 at an opticalmagnification of 20-fold using a detecting lens 8 with a focal length ofapproximately 4 mm, the photodiode 10 may be positioned a distance of 80mm from the detecting lens 8. Therefore, the optical system is renderedsubstantially more compact.

FIG. 6 is a top view of the detection part 4 provided with a secondembodiment of the optical system of the present invention. Parts of thestructure in common with the first embodiment are identified by the samereference numbers. The second embodiment of the optical system for aparticle analyzer is configured by an irradiation optical system 6,detecting lens 8, beam splitter 20, light shielding plate 9 disposed inthe light path of the light transmitted by the beam splitter 20,photodiode 10, light shielding plate 21 disposed in the light path ofthe light reflected by the beam splitter 20, and photodiode 22. Thelight path of the scattered light from the particles flowing through theflow cell 7 is indicated by a solid line. The path of the direct lightfrom the laser diode 61 is indicated by a dashed line.

The light transmitted by the beam splitter 20 follows the same lightpath as the first embodiment. That is, the direct light from the laserdiode 61 becomes a hyperelliptic beam converging in the horizontaldirection (x direction) and extending in the perpendicular direction (ydirection) at the third focusing point C at the position of the lightshielding plate 9. Therefore, this direct light is blocked by the lightshielding part 91 of the light shielding plate 9. The scattered lightfrom the particles passes through the circular aperture 92 of the lightshielding plate 9, and impinges the photodiode 10.

However, the direct light from the laser diode 61 reflected by the beamsplitter 20 becomes a hyperelliptic beam extending in the perpendiculardirection (y direction) similar to the third focusing point C at thethird focusing point C′ at the position of the light shielding plate 21.Therefore, the direct light is blocked by the light shielding part 211of the light shielding plate 21 shown in FIG. 7. The scattered lightfrom the particles passes through the circular aperture 212 of the lightshielding plate 21, and impinges the photodiode 22.

The light shielding plate 21 shown in FIG. 7 is provided with a lightshielding part 211 that is wider in width than the light shielding part91 of the light shielding plate 9 shown in FIG. 5. The minimumscattering angle of the scattered light passing through the circularaperture 212 of the light shielding plate 21 is greater than the minimumscattering angle of the scattered light passing through the circularaperture 91 of the light shielding plate 9. As a result, the photodiode22 receives scattered light from a greater minimum scattering angle thanthe photodiode 10.

A modification of the light shielding plate is shown in FIG. 8. Thelight shielding plate 21′ is provided with a light shielding part 211′that is wider in width than the light shielding part 91 of the lightshielding plate 9, and a circular aperture 212′ that has a largerdiameter than the circular aperture 92. Therefore, the minimumscattering angle and maximum scattering angle of the scattered lightpassing through the circular aperture 212′ are greater than the minimumscattering angle and maximum scattering angle of the scattered lightpassing through the circular aperture 92. As a result, the photodiode 22receives scattered light from both a larger minimum scattering angle andlarger maximum scattering angle than the photodiode 10.

A schematic drawing of the angle distribution of scatteringcharacteristics is shown in FIG. 9 to illustrate the scattering angles.The optimum scattering angle range differs depending on the size andrefractive index of the particle. When the refractive index n isdifferent at n1 and n2, the scattering characteristics change dependingon the size of the particle. Therefore, the detection range also changesto readily reflect the size of the particle. Samples that include aplurality of particles types having different scattering characteristicscan be measured using an optical system capable of detecting scatteredlight at different scattering angles, as in the second embodiment shownin FIG. 6.

The second embodiment is capable of easily detecting scattered lighthaving different scattering characteristics by respectively disposinglight shielding plate 9 and light shielding plate 21, which havedifferent scattering angle ranges for transmission light, at the thirdfocusing points C and C′ in the light path separated by the beamsplitter 20.

When a two-dimensional distribution diagram is created based on thesignal values of scattered light at different detectable scatteringangles detected by the photodiodes 10 and 22, the distribution may alsobe prepared with a dual axis for the signals values of the photodiode 10and signal values for the photodiode 22. A dual axis distributiondiagram using the signals values of the photodiodes 10 and 22 iseffective for illustrating the distribution hemoglobin content andvolume in erythrocytes.

FIG. 10 is a top view of the detection part 4 provided with a thirdembodiment of the optical system of the particle analyzer. Parts of thestructure in common with the previous embodiments are identified by thesame reference numbers. The third embodiment of the optical system for aparticle analyzer includes a dichroic mirror 23 and photomultiplier 24added to the first embodiment of the optical system for a particleanalyzer. The light path of the scattered light from the particlesflowing through the flow cell 7 is indicated by a solid line. The pathof the direct light from the laser diode 61 is indicated by a dashedline.

The dichroic mirror 23 has optical characteristics such that the lightnear the wavelength (approximately 635 nm) is the laser might emittedfrom the laser diode 61 is allowed to pass through, and light of longerwavelength than the laser light is reflected. That is, the longwavelength fluorescent light from the particles is reflected by thedichroic mirror 23. However, the direct light from the laser diode 61passes through the dichroic mirror 23. Therefore, there is no need toplace a light shielding member between the dichroic mirror 23 and thephotomultiplier 24 to block the direct light from the laser diode 61.The direct light transmitted through the dichroic mirror 23 is, however,blocked by the light shielding part 91 of the light shielding plate 9just as in the first embodiment. The scattered light from the particlespasses through the circular aperture 92 of the light shielding plate 9,and impinges the photodiode 10.

In the third embodiment, the forward fluorescent light can be detectedby the photomultiplier 24 without mediation by the light shieldingplate. Therefore, a reduction of fluorescent light intensity caused bythe light shielding plate is prevented. As a result, there is no needfor lenses and the like to focus the forward fluorescent light from theparticles, unlike when detecting forward fluorescent light. The opticalsystem can thus be rendered even more compact.

FIG. 11 is a top view of the detection part 4 provided with a fourthembodiment of the optical system of the particle analyzer. Parts of thestructure in common with the previous embodiments are identified by thesame reference numbers. The fourth embodiment of the optical system fora particle analyzer is configured by a collimator lens 25 for convertingthe scattered light from the particles passing through the flow cell 7to parallel rays, a beam splitter 20, a first detecting lens 26 disposedin the light path of the light transmitted through the beam splitter 20,light shielding plate 9, photodiode 10, second detecting lens 27disposed in the light path of the light reflected by the beam splitter20, light shielding plate 21, and photodiode 22. The light path of thescattered light from the particles flowing through the flow cell 7 isindicated by a solid line. The path of the direct light from the laserdiode 61 is indicated by a dashed line.

The direct light from the laser diode 61 passes through the collimatorlens 25 and impinges the beam splitter 20. The direct light transmittedthrough the beam splitter 20 is focused on the third focusing point C atthe position of the light shielding plate 9 by the first detecting lens26. The direct light focused on the third focusing point C is blocked bythe light shielding part 91 of the light shielding plate 9. Thescattered light from the particles passes through the collimator lens 25and impinges the beam splitter 20. The scattered light transmittedthrough the beam splitter 20 passes through the circular aperture 92 ofthe light shielding plate 9, and impinges the photodiode 10. However,the direct light reflected by the beam splitter 20 is focused on thethird focusing point C′ at the position of the light shielding plate 21by the second detecting lens 27. The direct light focused on the thirdfocusing point C′ is blocked by the light shielding part 211 of thelight shielding plate 21. The scattered light from the particles passesthrough the circular aperture 212 of the light shielding plate 21, andimpinges the photodiode 22.

In the fourth embodiment, the scattered light from the particles thathave passed through the flow cell 7 are once rendered parallel rays bythe collimator lens 25. Therefore, the position of the first detectinglens 26 which directs the parallel rays to the photodiode 10 can befreely moved on the optical axis of the laser diode 61. That is, thedistance from the collimator lens 25 to the first detecting lens 26 canbe freely set. Hence, it is possible to ensure adequate space for thedisposition of the beam splitter 20 and/or the dichroic mirror 23. Aplurality of beam splitters 20 can therefore be disposed to detectscattered light from three or more detectable scattering angles.Moreover, fluorescent light detection can be performed in parallel bypositioning the dichroic mirror 23 instead of a beam splitter 20.

Although the embodiment is illustrated using a single beam splitter 20in FIG. 11, the present invention is naturally not limited to deployinga single beam splitter. As described above, it is possible to deploy aplurality of beam splitters 20 and/or the dichroic mirrors 23.

FIG. 12 is a top view of the detection part 4 provided with a fifthembodiment of the optical system of the particle analyzer. Parts of thestructure in common with the previous embodiments are identified by thesame reference numbers. The configuration of the fifth embodiment of theoptical system for a particle analyzer is a modification in that thelight shielding plate 9 and first detecting lens 26 of the fourthembodiment are changed to a third detecting lens 29 having a blackcoating 28. The light shielding plate 21 and second detecting lens 27are also changed to a fourth detecting lens 30 having a black coating28. The light shielding member and detecting lens are integrated in asingle unit. Therefore, the optical axis is easily adjustable.

FIGS. 13 and 14 illustrate a sixth embodiment of the optical system fora particle analyzer. Parts of the structure in common with the firstembodiment are identified by the same reference numbers. The sixthembodiment of the optical system for a particle analyzer is amodification in which the convex cylindrical lens 63 of the irradiationoptical system of the first embodiment is changed to a concavecylindrical lens 65. FIG. 13 is a side view of the detection part 4, andFIG. 14 is a top view (viewed from the top of the diagram) of thedetection part 4.

When viewing the detection part 4 from the side (refer to FIG. 13), theradial laser light emitted from the laser diode 61 is converted toparallel rays by the collimator lens 62. These parallel rays are notrefracted as they pass through the concave cylindrical lens 65. Theparallel rays that have passed through the concave cylindrical lens 65are focused at a first focusing point A in the center of the particleflow of the flow cell 7 by the detecting lens 64. The direct light thathas passed through the first focusing point A is masked by the lightshielding plate 9. However, the scattered light from the particles isfocused by the detecting lens 8 and impinges the photodiode 10.

When viewing the detection part 4 from above (refer to FIG. 14), theradial laser light emitted from the laser diode 61 is converted toparallel rays by the collimator lens 62. These parallel rays arerefracted in a horizontal direction outside the optical axis as theypass through the concave cylindrical lens 65. Then, the light refractedby the concave cylindrical lens 65 is focused on the third focusingpoint C on the photodiode 10 side by the collimator lens 64. That is,the third focusing point C can be formed between the photodiode 10 andthe detecting lens 8 by the concave cylindrical lens 65 unconnected to asecond focusing point B disposed between the light source and the flowcell 7. Therefore, there is no need to deploy the light shielding plate9 between the flow cell 7 and the detecting lens 8. Moreover, adetecting lens 8 having a short focal length may be used. The opticalsystem can therefore be rendered far more compact.

Although described by way of examples of embodiments, the presentinvention is not limited to these embodiments.

The particles in the present invention are not particularly limitedinsofar as the particles can pass through a flow cell. Specific examplesof particles include hemocytes such as erythrocytes, leukocytes, orplatelets contained in blood, tangible materials such as bacteria,erythrocytes, leukocytes epidermal cells, or columnar epitheliumcontained in urine, and particles or powder such as toners and pigmentsand the like.

The flow cell used in the present invention is not particularly limitedinsofar as optical information can be obtained from particles passingthrough the interior of the flow cell. For example, transparentmaterials having a smooth surface are desirable. Specific examplesinclude glass and the like.

The particle analyzer in the present invention is not particularlylimited insofar as the analyzer detects optical information fromparticles passing through a flow cell using an optical flow cytometricmethod, and analyzes the morphological information of the particlesbased on the detected optical information. Examples of particleanalyzers include blood analyzers, urine analyzers, toner analyzers, andpigment analyzers, among which blood analyzers and urine analyzers aredesirable.

The light source used in the present invention is not particularlylimited insofar as the light source is capable of emitting light.Examples of light sources include semiconductor lasers, argon lasers andthe like.

The light from the particles in the present invention is notparticularly limited insofar as such light is detectable by aphotodetector. Examples of such detectable light include fluorescence,absorptivity, and light loss. Scattered light and fluorescent light areparticularly desirable.

The irradiation optical system used in the present invention is notparticularly limited insofar as the irradiation optical system iscapable of forming a first focusing point that focuses light from alight source on particles passing through a flow cell, a second focusingpoint that focuses light from a light source at a position between adetecting lens and a photodetector. It is desirable that the irradiationoptical system has at least one cylindrical lens. The first focusingpoint is desirably an elliptic spot that converges the light from alight source in a perpendicular direction (direction linear on theoptical axis of the laser beam and parallel to the channel of theparticles passing through the flow cell), and extends in a horizontaldirection (direction linear on the optical axis of the laser beam, andlinear to the channel of the particles passing through the flow cell).The second focusing point is desirably an elliptic spot converging inthe horizontal direction, and extending in the perpendicular direction.

The photodetector used in the present invention is not particularlylimited insofar as the photodetector is capable of photoelectricconversion of optical information to obtain light signals. Examples ofsuch photodetectors include photodiodes, avalanche photodiodes,phototransistors, and photomultipliers. Photodiodes are desirable whendetecting scattered light, and avalanche photodiodes andphotomultipliers are desirable when detecting fluorescence.

The light shielding member used in the present invention is notparticularly limited insofar as the light shielding member can block thetransmission light passing through a flow cell without scattering thelight from the light source by the particles. Examples include lightshielding members provided with a wire-like light shielding part in thecenter of a circular aperture, and detecting lens with a black coatedsurface.

Various configurations of the above embodiments may be used in mutualcombinations. When a plurality of configurations are included in asingle embodiment, one or a plurality of configurations may be suitablyselected from among the embodiments and used individually or incombination in the optical system of the present invention.

The foregoing detailed description and examples have been provided byway of explanation and illustration, and are not intended to limit thescope of the appended claims. Many variations in the presently preferredembodiments will be obvious to one of ordinary skill in the art, andremain within the scope of the appended claims and their equivalents.

1. An optical system for a particle analyzer, comprising: a light sourceconfigured to irradiate light to particles passing through a flow cell;a photodetector configured to receive light scattered from theparticles; a detecting lens, which is disposed between the flow cell andthe photodetector, configured to direct the light scattered from theparticle toward the photodetector; a light shielding plate, which isdisposed between the detecting lens and the photodetector, configured toblock the light coming directly from the light source from entering thephotodetector and having a first and a second apertures and an elongatedlight shielding part which is arranged between the first and secondapertures; and an irradiation optical system, disposed between the lightsource and the flow cell.
 2. The optical system for the particleanalyzer of claim 1, wherein the elongated light shielding part extendsin parallel to a direction in which the particles pass through the flowcell.
 3. The optical system for the particle analyzer of claim 1,wherein the irradiation optical system forms a first focus at the flowcell through which the particles pass and forms with the detecting lensa second focus at the elongated light shielding part.
 4. The opticalsystem for the particle analyzer of claim 3, wherein the first focusconverges in parallel to a direction in which the particles pass throughthe flow cell and extends perpendicular to the direction in which theparticles pass through the flow cell, and the second focus convergesperpendicular to the direction in which the particles pass through theflow cell and extends in parallel to the direction in which theparticles pass though the flow cell.
 5. The optical system for theparticle analyzer of claim 1, further comprising: a beam splitterdisposed between the detecting lens and the light shielding plate andconfigured to split the light scattered from the particles; a secondphotodetector configured to receive a beam of split light from beamsplitter; and a second light shielding plate disposed between the beamsplitter and the second photodetector and having a third and a fourthapertures and a second elongated light shielding part which is arrangedbetween the third and fourth apertures.
 6. The optical system for theparticle analyzer of claim 1, further comprising: a dichroic mirrordisposed between the detecting lens and the light shielding plate andconfigured to selectively pass therethrough only the light of aparticular wavelength coming from the particles and reflect away thelight of other wavelengths; and a fluorescence detector configured toreceive the light of other wavelengths reflected by the dichroic mirror.7. The optical system for the particle analyzer of claim 1, wherein thelight shielding plate is quadrangle in shape.
 8. The optical system forthe particle analyzer of claim 1, wherein the first and second aperturesare similar in shape to each other.
 9. A particle analyzer, comprising:a flow cell through which particles pass; a light source configured toirradiate light to the particles passing through the flow cell; aphotodetector configured to receive the light scattered from theparticles; a detecting lens, which is disposed between the flow cell andthe photodetector, configured to direct the light scattered from theparticle toward the photodetector; a light shielding plate, which isdisposed between the detecting lens and the photodetector, configured toblock the light coming directly from the light source from entering thephotodetector and having a first and a second apertures and an elongatedlight shielding part which is arranged between the first and secondapertures; an irradiation optical system disposed between the lightsource and the flow cell; and an analyzing part configured to analyzethe particles based on detection results from the photodetector.
 10. Theparticle analyzer of claim 9, wherein the elongated light shielding partextends in parallel to a direction in which the particles pass throughthe flow cell.
 11. The particle analyzer of claim 9, wherein theirradiation optical system forms a first focus at the flow cell throughwhich the particles pass and forms with the detecting lens a secondfocus at the elongated light shielding part.
 12. The particle analyzerof claim 11, wherein the first focus converges in parallel to adirection in which the particles pass through the flow cell and extendsperpendicular to the direction in which the particles pass through theflow cell, and the second focus converges perpendicular to the directionin which the particles pass through the flow cell and extends inparallel to the direction in which the particles pass through the flowcell.
 13. The particle analyzer of claim 9, further comprising: a beamsplitter disposed between the detecting lens and the light shieldingmember and configured to split the light scattered from the particles; asecond photodetector configured to receive a beam of the split lightfrom the beam splitter; and a second light shielding plate disposedbetween the beam splitter and the second photodetector and having athird and fourth apertures and a second elongated light shielding partwhich is arranged between the third and fourth apertures.
 14. Theparticle analyzer of claim 9, further comprising: a dichroic mirrordisposed between the detecting lens and the light shielding plate andconfigured to selectively pass therethrough only the light of aparticular wavelength coming from the particles and reflect away thelight of other wavelengths; and a fluorescence detector configured toreceive the light of other wavelengths reflected by the dichroic mirror.15. The particle analyzer of claim 9, wherein the light shielding plateis quadrangle in shape.
 16. The particle analyzer of claim 9, whereinthe first and second apertures are similar in shape to each other.
 17. Ablood analyzer, comprising: a flow cell through which blood cells pass;a light source configured to irradiate light to the blood cells passingthrough the flow cell; a photodetector configured to receive the lightscattered by the blood cells; a detecting lens, which is disposedbetween the flow cell and the photodetector, configured to direct thelight scattered from the blood cell toward the photodetector; a lightshielding plate, which is disposed between the detecting lens and thephotodetector, configured to block the light coming directly from thelight source from entering the photodetector and having a first and asecond apertures and an elongated light shielding part which is arrangedbetween the first and second apertures; an irradiation optical systemdisposed between the light source and the flow cell; and an analyzingpart configured to analyze the blood cells based on detection resultsfrom the photodetector.
 18. The blood analyzer of claim 17, wherein theelongated light shielding part extends in parallel to a direction inwhich the particles pass through the flow cell.
 19. The blood analyzerof claim 17, wherein the irradiation optical system forms a first focusat the flow cell through which the particles pass and forms with thedetecting lens a second focus at the elongated light shielding part. 20.The blood analyzer of claim 17, wherein the first focus converges inparallel to a direction in which the blood cell pass through the flowcells and extends perpendicular to the direction in which the bloodcells pass through the flow cell, and the second focus convergesperpendicular to the direction in which the blood cells pass through theflow cell and extends in parallel to the direction in which the bloodcell pass through the flow cell.